Electronic ignition control modules for providing input pulses to an automobile ignition coil's primary circuit are well-known. Such electronic ignition control modules have been in common use since 1974. They generally replace the cam and contact breaker points assembly utilized in earlier automobiles since this assembly is subject to wear and requires frequent maintenance.
A further disadvantage of utilizing conventional contact point type ignition systems is that the higher the RPM of the engine, the less time the points are closed. This decreases the secondary voltage of the ignition coil as well as the ignition on time and ignition primary current at higher RPM's. The end result is a decrease in the ignition spark quality within the combustion chamber which causes poor engine performance and an increase in exhaust emissions.
A yet further disadvantage of conventional contact points is that in such conventional ignition systems, the opening and closing of the contact points is relatively slow in comparison to the speed with which newer electronic ignition control module systems operate. Thus, engine performance is substantially better in automobiles utilizing the newer electronic ignition control module systems.
General Motors Corporation installed the first discrete electronic ignition system on vehicles in 1970. The remaining domestic car manufacturers installed electronic ignition systems in 1973 and 1974, either utilizing discrete electronics or micro processors. Vehicles imported into the U.S.A. presently utilize an electronic ignition system in order to meet E.P.A. requirements.
The signal that is generated by the pick-up coil to turn the control module on and off is either generated with an AC pick-up coil mounted in the distributor, at the crank shaft harmonic balancer or by using a Hall Effect sensor in the distributor to develop a square waveform. The AC generator pick-up coil produces a cosecant sine wave.
When the control module sees an AC ripple going from a positive to a negative or a negative to a positive voltage, it will trigger the ignition coil. A Hall Effect sensor, at either the crankshaft or within the distributor, will create the same positive or negative waveform causing the control module to turn on and off.
There are similarities among all control modules, particularly in their function or operation. In all control modules a signal from an outside source is required. The outside source is typically either an AC signal or Hall Effect transducer which is utilized to trigger the control module. Some control modules must have a north seeking magnetic field to properly trigger the control module. Others require a south seeking magnetic field. Within the control module is typically disposed a spark timing monitoring circuit, a lock prevention circuit, a duty control circuit, a current limiting circuit, a power switching circuit, an advance circuit, a retard circuit, and a dynamic knock circuit. Some control modules will have all of these circuits, while others may have just one or two of these circuits, depending upon the design characteristics of the particular control module.
A spark timing signal monitoring circuit monitors and amplifies the signal from the distributor pick-up coil. When this circuit is damaged, the resulting erratic timing causes poor fuel economy, higher exhaust emissions, etc.
A lock-preventing circuit cuts off the ignition coil primary circuit current when the ignition is on and the engine is not running. A problem with the lock-generating circuit could cause a no start condition.
A duty control circuit controls the ratio of ignition coil primary current on-off time, equivalent to dwell angle. This circuit is RPM sensitive and if it is damaged dwell control will be lost.
A power switching circuit creates or breaks primary circuit current flow of the ignition coil. A failure in this circuit can cause the ignition system to become inoperative.
A current limiting circuit prevents excessive current from entering the power switching circuit. A failure in this circuit can cause damage to either the power switching circuit or to the ignition coil's primary winding.
The PIP assembly generates a signal which indicates crank shaft position and RPM. The PIP signal is supplied to and processed by the electronic ignition control module.
The electronic control module outputs an EST/SPOUT signal that is transmitted back to the electronic ignition module to control ignition timing, i.e., to advance or retard timing.
There are various input transducers and engine sensors that monitor different engine calibrations. These sensors provide input signals into the computer electronic ignition control module such as throttle position, engine speed, coolant temperature, intake manifold vacuum, and throttle position status. These input signals are processed by the computer or microprocessor of the electronic ignition control module which then determines the precise instant at which the ignition pulse (spark) is to be provided.
The points, condenser, and cam lobe of earlier automobile engines are replaced by an AC magnetic induction pick-up coil or a Hall Effect square waveform generator which turns the electronic ignition control module on and off depending on the RPM of the engine. The faster the reluctor or armature spins inside the pick-up coil, the correspondingly faster the pulse rate to turn the electronic ignition control module on and off becomes. This AC pulse turning the electronic ignition control module on and off is what turns the primary circuit of the ignition coil on and off.
This AC pulse is not effected by current or by wear such as are conventional point contacts wherein the rubbing block that the points are mounted to invariably wears down, consequently changing the dwell and thereby changing the timing. Such conventional contact points are also limited as to the amount of current that they are capable of handling.
However, this is not the case with electronic ignition control module systems. The rotation of the armature within the pick-up coil generates an AC ripple every time it passes a pyramid on the pick-up coil. There are as many pyramids both on the pick-up coil and on the reluctor as there are cylinders. For example, a four cylinder engine has four pyramids, on both the coil and on the reluctor, one pair for each cylinder. The faster the armature revolves within the pick-up coil, the faster the primary winding of the coil through the electronic ignition control module is triggered.
Electronic ignition control modules are solid state and may be embodied as either discrete or thick film. Either embodiment will contain and utilize various transistors, resistors, thermistors, Darlington gate circuits, etc.
The conventional ignition system could not induce enough primary ignition current into the coil at elevated RPM, therefore if the primary current was not saturating the primary winding of the ignition coil, then there would not be sufficient current at the spark plug. There is not enough time to electrically saturate the primary winding of the coil. In electronic ignition control modules, this problem does not exist. Transistors can inherently trigger much faster than the mechanical points.
Electronic ignition systems are generally referred to as high energy ignition systems. The basic function of the electronic ignition circuit is to permit a very rapid build up of current in the primary winding of the ignition coil. The function of the pick-up coil is to very rapidly interrupt the flow of that current such that the resulting fly back action will then induce the required high secondary voltage needed for the spark energy within the secondary winding of ignition coil, regardless of the RPM or speed of the engine.
There are currently two basic types of electronic ignition control modules designs. In the first type, a fixed dwell design is preset within the control module and in the second type, the dwell depends upon engine RPM. The fixed dwell will generally be in the neighborhood of 2 to 4 amps irrespective of engine RPM.
The varied dwell is sensitive to engine RPM. At very low RPM the need for primary current is low. Therefore, there is low current into the primary of the coil. High RPM or high engine speeds will provide high dwell or high current flowing through the control module.
Proper testing of an electronic ignition control module involves relatively complex troubleshooting procedures which are performed upon the automobile with the electronic ignition control module in place. A less rigorous and consequently less determinative method of troubleshooting potential electronic ignition control module problems consist of replacement of the electronic ignition control module in order to eliminate the symptoms of the problem.
However, contemporary methods of troubleshooting, i.e., rigorous testing and removal/replacement, have inherent deficiencies. Rigorous testing of the electronic ignition control module requires skill, proper test equipment, and a substantial amount of time. Such rigorous testing requires that a technician be adequately trained in the art of electronic troubleshooting and that the technician use sophisticated test equipment. The procedures and test equipment required generally vary among automobile manufacturers, further complicating the matter.
Removal and replacement of an electronic ignition control module as a troubleshooting procedure is often inadequate in that elimination of the problem often cannot be verified immediately and the use of a known good substitute ignition control module is required. It is not always possible to immediately verify elimination of the symptoms of the problem due to the fact that such symptoms are frequently intermittent in nature and thus often occur only under very specific conditions. Indeed, the symptoms may occur at random or seemingly random instances. Thus, after removal and replacement of the suspect electronic ignition control module, the automobile may have to be operated for many hours to verify eradication of the problem.
As mentioned above, removal and replacement of a suspect electronic ignition control module requires that a substitute, known-good, electronic ignition control module be provided. Not only does this generally require that such an electronic ignition control module be purchased, but also that the purchased electronic ignition control module be utilized for a substantial period of time, thus prohibiting return of the electronic ignition control module in the event that the symptoms of the problem are not eliminated thereby. Generally, automotive supply sources are reluctant to accept returns on such electronic devices since they are unable to verify their working condition.
Even so, the popular solution in the prior art when a defective electronic ignition control module is suspected, is to purchase a new unit and to remove/replace the suspect unit. This is done without knowing the validity of the test procedure until such time as elimination of the problem symptoms is verified.
Electronic ignition control module testers are also known wherein an electronic ignition control module is connected thereto and various different aspects of the electronic ignition control module are tested thereby. However, such electronic ignition control module testers are generally utilized by electronic ignition control module manufacturers to test only those specific electronic ignition control modules manufactured thereby. Electronic ignition control module testers which are intended to test electronic ignition control modules from a variety of different manufacturers, i.e., of a variety of different types, utilize comparatively complex cabling so as to facilitate electrical connection to the electronic ignition control module.
Such general purpose electronic ignition control module testers further require that the user define the proper sequence of tests, appropriate for the particular electronic ignition control module type being tested, and as such are comparatively complex to use.
Although the prior art has recognized the need for electronic ignition control module troubleshooting procedures and test equipment, such procedures and test equipment have to date been inadequate in providing a satisfactory remedy. Contemporary electronic ignition control module testers are either specifically intended for use with a particular electronic ignition control module type or require complex connections to the electronic ignition control module to be tested and complex definition of the tests to be performed thereon. It is thus extremely difficult, if not impossible, for untrained personnel to perform such tests in an efficient and reliable manner. As such, it is desirable to provide a simpler, more reliable means for testing electronic ignition control modules in order to verify their operational capabilities.